Perpetual calendar



FIG. 1 is a perspective view of a perpetual calendar showing my new design.

FIG. 2 is a front elevational view, the opposite side thereof being plain and unornamental;

FIG. 3 is a right side elevational view;

FIG. 4 is a top right plan view; and

FIG. 5 is a bottom plan view. 

The ornamental design for a perpetual calendar, substantially as shown and described. 